This invention relates to a novel textile filament having improved properties including soil resistance, resilience, torsional recovery, static dissipation, bulk, dielectric and acoustical qualities and luminosity combined with a high luster. More specifically, it relates to a filament containing a plurality of continuous internal cavities of predetermined size, shape, position and orientation to provide a filament with the aforesaid properties and characteristics.
The characteristic and highly desirable luster or light reflective properties of conventional solid synthetic filaments having a round cross-sectional shape is considerably dulled by the incorporation of pigmentary coloring matter. In order to restore some of this luster, it has previously been proposed to form synthetic filaments in non-round cross-sectional shape, such as described, for example, in U.S. Pat. Nos. 2,939,201, 3,425,893, 3,499,958 and 3,508,390. A number of non-round cross-sectional shapes have been utilized, including, for example, triangular cruciform, H-shaped, Y-shaped and trilobal. In general, these cross-sectional shapes exhibit a high degree of light reflectance which results in the appearance of luster. In addition to providing luster, the light reflectance of the non-round cross-sectional shape of the filaments visually masks the presence of soil on the surface of the filament. However, with most of the desirable cross-sections, there are concavities or crevices on the surface in which soil, detergents and other foreign matter become trapped and cannot readily be removed by normal cleaning. As soil accumulates in these cavities, the light reflectance is gradually destroyed, and both the luster and the soil hiding characteristics of the filaments are lost.
It has been proposed to overcome the soiling problem by providing internal cavities within the filament. U.S. Pat. No. 3,745,061 teaches the preparation of such a filament. However, this reference teaches that where a bright filament luster is desired, the filaments should have flattened sides and rounded corners. Additionally, for maximum luster, the reference discloses that the filaments should contain less than 0.5% of an opaque pigment.
It has also been proposed to make filaments having cavities therein as disclosed, for example, in U.S. Pat. Nos. 2,965,925, 3,493,459, 3,558,420 and 3,745,061. One problem with such filaments is that as the cavity volume increases the bending stiffness and torsional rigidity decreases, thereby adversely affecting the resilience of the filament.